#include <iostream>
#define int unsigned long long

using namespace std;

int dp[100] = {1, 1};
signed main() {
    int num;
    while (cin >> num) {
        for (int i = 2; i <= num; ++ i) {
            dp[i] = dp[i - 2] + dp[i - 1];
        }
        cout << dp[num] << endl;
    }
    return 0;
}